APOD: Mars, Ceres, Vesta (2014 Apr 10)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3547
Joined: Fri Dec 04, 2009 3:27 am

APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by APOD Robot » Thu Apr 10, 2014 4:06 am

Image Mars, Ceres, Vesta

Explanation: That bright, ruddy star you've recently noticed rising just after sunset isn't a star at all. That's Mars, the Red Planet. Mars is now near its 2014 opposition (April 8) and closest approach (April 14), looping through the constellation Virgo opposite the Sun in planet Earth's sky. Clearly outshining bluish Spica, alpha star of Virgo, Mars is centered in this labeled skyview from early April, that includes two other solar system worlds approaching their opposition. On the left, small and faint asteroid Vesta and dwarf planet Ceres are seen near star Tau Virginis. But you'll just have to imagine NASA's Dawn spacecraft cruising between the small worlds. Having left Vesta in September of 2012, Dawn's ion engine has been steadily driving it to match orbits with Ceres, scheduled to arrive there in February 2015. Of course, you can also look near Mars for the Moon opposite the Sun in Earth's sky on the night of April 14/15 ... and see a total lunar eclipse.

<< Previous APOD This Day in APOD Next APOD >>
[/b]

Boomer12k
:---[===] *
Posts: 2483
Joined: Sun Apr 22, 2007 12:07 am

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by Boomer12k » Thu Apr 10, 2014 8:32 am

And they watch us with Envious Eyes.....


Nice depiction of things.

:---[===] *

User avatar
orin stepanek
Plutopian
Posts: 4790
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by orin stepanek » Thu Apr 10, 2014 11:28 am

I like the way Ceres and Vesta were circled; I never would have found them on my own! :D
Orin

Smile today; tomorrow's another day!

BDanielMayfield
Don't bring me down
Posts: 1968
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by BDanielMayfield » Thu Apr 10, 2014 11:39 am

orin stepanek wrote:I like the way Ceres and Vesta were circled; I never would have found them on my own! :D
Yes. I wonder what their apparent magnitudes are? Looks like they might be easy to find with binoculars.
"Happy are the peaceable ... "

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15967
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by neufer » Thu Apr 10, 2014 11:43 am

BDanielMayfield wrote:
orin stepanek wrote:
I like the way Ceres and Vesta were circled; I never would have found them on my own! :D
Yes. I wonder what their apparent magnitudes are? Looks like they might be easy to find with binoculars.
  • Vesta should be magnitude ~5 and Ceres ~7.
http://dawn.jpl.nasa.gov/mission/live_shots.asp wrote:

Where is Dawn Now?

Want to know how far away Dawn is, or how fast it is traveling? These questions have multiple answers since the answer depends on what you use as a reference frame.

The Dawn trajectory is color-coded to provide information about when Dawn is using one of its ion thrusters and when it is coasting. The orbits of Earth, Mars, Vesta and Ceres are also given. The other four views use Dawn as a reference point, as if you were near the spacecraft looking at the Sun, Ceres, Earth, and Vesta. These views show the spacecraft in its true orientation as though you were viewing each given object. If the plasma trail is present, an ion thruster is operating; if the trail is not present, Dawn is coasting. The images are updated regularly with time given in UTC.
Art Neuendorffer

CURRAHEE CHRIS
Science Officer
Posts: 104
Joined: Mon Sep 30, 2013 4:04 pm
Location: Mechanicsburg Pa.

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by CURRAHEE CHRIS » Thu Apr 10, 2014 12:39 pm

Very timely picture for me as I think I am beginning to apply some of the things I am learning from this forum to actual skywatching- I live in Pennsylvania- would Spica be visible to the naked eye? I believe it has been (when we've had clear skies) the last couple evenings. Could someone confirm that it would be possible to see Spica with the naked eye? If so, I will feel happy as I have learned and applied some new knowledge. :D :ssmile:

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15967
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Mars at Opposition

Post by neufer » Thu Apr 10, 2014 1:38 pm

Click to play embedded YouTube video.
Art Neuendorffer

User avatar
BMAONE23
Commentator Model 1.23
Posts: 4076
Joined: Wed Feb 23, 2005 6:55 pm
Location: California

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by BMAONE23 » Thu Apr 10, 2014 2:03 pm

CURRAHEE CHRIS wrote:Very timely picture for me as I think I am beginning to apply some of the things I am learning from this forum to actual skywatching- I live in Pennsylvania- would Spica be visible to the naked eye? I believe it has been (when we've had clear skies) the last couple evenings. Could someone confirm that it would be possible to see Spica with the naked eye? If so, I will feel happy as I have learned and applied some new knowledge. :D :ssmile:
WIKI wrote:Spica (α Vir, α Virginis, Alpha Virginis, pronounced /ˈspaɪkə/) is the brightest star in the constellation Virgo, and the 15th brightest star in the night sky. It is a blue giant and a variable star of the Beta Cephei type located 260 light years from Earth.

At an apparent magnitude of just over +1, and being the 15th brightest star in the night sky. Spica is clearly Naked Eye visible

CURRAHEE CHRIS
Science Officer
Posts: 104
Joined: Mon Sep 30, 2013 4:04 pm
Location: Mechanicsburg Pa.

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by CURRAHEE CHRIS » Thu Apr 10, 2014 2:16 pm

BMAONE23 wrote:At an apparent magnitude of just over +1, and being the 15th brightest star in the night sky. Spica is clearly Naked Eye visible
Thank you for that. I feel like an accomplished star gazer now!! :D :D Spica will now hold a very treasured spot in my newborn star gazing career. Outside of the little dipper and Orion's belt, this is the first object i've learned about and been able to find in the sky. Wish I could go back to the Lowell Observatory, find the professor who said "you are smart enough to do this" (when I told him this was a hobby well over my IQ) and tell him I did it- this one time!! :lol2:

Best regards
CC

User avatar
Anthony Barreiro
Turtles all the way down
Posts: 793
Joined: Wed May 11, 2011 7:09 pm
Location: San Francisco, California, Turtle Island

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by Anthony Barreiro » Thu Apr 10, 2014 2:25 pm

This is a lovely picture, and a very exciting astronomical conjunction! I've been watching Vesta and Ceres in 56 mm binoculars for the past few weeks. At 6th magnitude Vesta is easy to identify even in my light polluted city. Ceres has brightened from 8th to 7th magnitude, but is still tough to pick out in the city. On Saturday night our astronomy club had our monthly public star party at a less light-polluted location, and that helped, but there's still a lot of stars that are about as bright as Ceres in a binocular field of view. I hope To have a few clear nights in a row so I can sketch and see which star moves.
May all beings be happy, peaceful, and free.

User avatar
Anthony Barreiro
Turtles all the way down
Posts: 793
Joined: Wed May 11, 2011 7:09 pm
Location: San Francisco, California, Turtle Island

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by Anthony Barreiro » Thu Apr 10, 2014 2:33 pm

CURRAHEE CHRIS wrote:
BMAONE23 wrote:At an apparent magnitude of just over +1, and being the 15th brightest star in the night sky. Spica is clearly Naked Eye visible
Thank you for that. I feel like an accomplished star gazer now!! :D :D Spica will now hold a very treasured spot in my newborn star gazing career. Outside of the little dipper and Orion's belt, this is the first object i've learned about and been able to find in the sky. Wish I could go back to the Lowell Observatory, find the professor who said "you are smart enough to do this" (when I told him this was a hobby well over my IQ) and tell him I did it- this one time!! :lol2:

Best regards
CC
Chris, knowing the sky and learning astrophysics are very different skills. They both have their pleasures. I personally find skywatching inherently enjoyable, while anything that involves math provides more of a deferred gratification. But even the math is starting to grow on me.

Congratulations as you start to create your mental map of the sky, and your personal calendar of the year.
May all beings be happy, peaceful, and free.

User avatar
MarkBour
Subtle Signal
Posts: 891
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by MarkBour » Thu Apr 10, 2014 3:29 pm

Okay, speaking of math, and the Dawn spacecraft, I have a very basic orbital mechanics question. Actually, I'm not wanting the equations, just the qualitative description. Let's say I'm the Dawn spacecraft and I'm orbiting the Sun, a little ways in front of or behind the Earth, but in an identical orbit. Now, let's say I turn on my thruster to increase my forward motion. What happens? I believe I go into an elliptical orbit, with Earth's orbit as the perihelion and some larger distance as the aphelion. And oddly enough, although I accelerated "forward" and increased my forward rotational velocity (e.g. in km/s) around the Sun, instead of catching up to Earth, since I am now in a larger orbit, I will have watched the Earth pull ahead of me, in its steady journey around the Sun. So my rotational velocity in terms of degrees/s around the Sun actually decreased. Is that correct? So, in the diagram in the link to the Dawn spacecraft's mission, the transfer orbits actually show Dawn kind of backpedalling away from the planet it is at, as it transfers outward to a more Sun-remote planet's orbit?

It's counter-intuitive to me. Does anyone have a simulator for it?
Mark Goldfain

FloridaMike
Science Officer
Posts: 413
Joined: Fri Nov 04, 2011 2:21 pm
Location: Florida, USA

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by FloridaMike » Thu Apr 10, 2014 3:48 pm

MarkBour wrote:Okay, speaking of math, and the Dawn spacecraft, I have a very basic orbital mechanics question. Actually, I'm not wanting the equations, just the qualitative description. Let's say I'm the Dawn spacecraft and I'm orbiting the Sun, a little ways in front of or behind the Earth, but in an identical orbit. Now, let's say I turn on my thruster to increase my forward motion. What happens? I believe I go into an elliptical orbit, with Earth's orbit as the perihelion and some larger distance as the aphelion. And oddly enough, although I accelerated "forward" and increased my forward rotational velocity (e.g. in km/s) around the Sun, instead of catching up to Earth, since I am now in a larger orbit, I will have watched the Earth pull ahead of me, in its steady journey around the Sun. So my rotational velocity in terms of degrees/s around the Sun actually decreased. Is that correct? So, in the diagram in the link to the Dawn spacecraft's mission, the transfer orbits actually show Dawn kind of backpedalling away from the planet it is at, as it transfers outward to a more Sun-remote planet's orbit?

It's counter-intuitive to me. Does anyone have a simulator for it?
A really fun way to get to a more intuitive understanding of orbital dynamics is to read "The Smoke Ring" series by Larry Niven

EDIT ** The first book is called "The Integral Trees" **
Certainty is an emotion. So follow your spindle neurons.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15967
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by neufer » Thu Apr 10, 2014 4:06 pm

MarkBour wrote:
Let's say I'm the Dawn spacecraft and I'm orbiting the Sun, a little ways in front of or behind the Earth, but in an identical orbit. Now, let's say I turn on my thruster to increase my forward motion. What happens? I believe I go into an elliptical orbit, with Earth's orbit as the perihelion and some larger distance as the aphelion. And oddly enough, although I accelerated "forward" and increased my forward rotational velocity (e.g. in km/s) around the Sun, instead of catching up to Earth, since I am now in a larger orbit, I will have watched the Earth pull ahead of me, in its steady journey around the Sun. So my rotational velocity in terms of degrees/s around the Sun actually decreased. Is that correct? So, in the diagram in the link to the Dawn spacecraft's mission, the transfer orbits actually show Dawn kind of backpedaling away from the planet it is at, as it transfers outward to a more Sun-remote planet's orbit?
A normal spacecraft would indeed "go into an elliptical orbit, with Earth's orbit as the perihelion and some larger distance as the aphelion." Since its orbital period is now longer it will, indeed, watch the Earth eventually catch up and pass it (angularly) "from below" (i.e., closer to the sun) before reaching its aphelion.

However, the Dawn spacecraft produces a constant thrust such that it continues to spiral out. You will watch the Earth eventually catch up and pass you (angularly) from below (i.e., closer to the sun) but it will take somewhat longer.
Art Neuendorffer

NGC3314
Telescope Nerd
Posts: 114
Joined: Thu Sep 23, 2010 5:15 pm

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by NGC3314 » Thu Apr 10, 2014 6:36 pm

FloridaMike wrote:[

A really fun way to get to a more intuitive understanding of orbital dynamics is to read "The Smoke Ring" series by Larry Niven

EDIT ** The first book is called "The Integral Trees" **
Niven's inimitable short form:
East takes you Out, Out takes you West, West takes you In, In takes you East.
(This applies to definitions such that orbits go west-to-east, as almost all Earth satellites and large solar system objects do).

User avatar
MarkBour
Subtle Signal
Posts: 891
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by MarkBour » Thu Apr 10, 2014 6:49 pm

neufer wrote: . . . the Dawn spacecraft produces a constant thrust such that it continues to spiral out. You will watch the Earth eventually catch up and pass you (angularly) from below (i.e., closer to the sun) but it will take somewhat longer.
Thanks for the reply, and verification! I had heard of an ion thruster as a really far-out sci-fi idea when I was young. Then it never seemed to have materialized after many years as a practical technology. Bravo, NASA!

... Oh, and yes, I think it's high time I went and read some Larry Niven. :-)
Mark Goldfain

User avatar
Anthony Barreiro
Turtles all the way down
Posts: 793
Joined: Wed May 11, 2011 7:09 pm
Location: San Francisco, California, Turtle Island

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by Anthony Barreiro » Thu Apr 10, 2014 7:23 pm

NGC3314 wrote:Niven's inimitable short form:
East takes you Out, Out takes you West, West takes you In, In takes you East.
(This applies to definitions such that orbits go west-to-east, as almost all Earth satellites and large solar system objects do).
Oh, that's brilliant. I've got my koan for the day.
May all beings be happy, peaceful, and free.

User avatar
neufer
Vacationer at Tralfamadore
Posts: 15967
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by neufer » Thu Apr 10, 2014 9:59 pm

neufer wrote:
MarkBour wrote:
Let's say I'm the Dawn spacecraft and I'm orbiting the Sun, a little ways in front of or behind the Earth, but in an identical orbit. Now, let's say I turn on my thruster to increase my forward motion. What happens? I believe I go into an elliptical orbit, with Earth's orbit as the perihelion and some larger distance as the aphelion. And oddly enough, although I accelerated "forward" and increased my forward rotational velocity (e.g. in km/s) around the Sun, instead of catching up to Earth, since I am now in a larger orbit, I will have watched the Earth pull ahead of me, in its steady journey around the Sun. So my rotational velocity in terms of degrees/s around the Sun actually decreased. Is that correct? So, in the diagram in the link to the Dawn spacecraft's mission, the transfer orbits actually show Dawn kind of backpedaling away from the planet it is at, as it transfers outward to a more Sun-remote planet's orbit?
A normal spacecraft would indeed "go into an elliptical orbit, with Earth's orbit as the perihelion and some larger distance as the aphelion." Since its orbital period is now longer it will, indeed, watch the Earth eventually catch up and pass it (angularly) "from below" (i.e., closer to the sun) before reaching its aphelion.

However, the Dawn spacecraft produces a constant thrust such that it continues to spiral out. You will watch the Earth eventually catch up and pass you (angularly) from below (i.e., closer to the sun) but it will take somewhat longer.
http://en.wikipedia.org/wiki/Lituus_%28mathematics%29 wrote:
<<In mathematics, a lituus is a spiral in which the angle is inversely proportional to the square of the radius (as expressed in polar coordinates).

Image

The curve was named for the ancient Roman lituus by Roger Cotes in a collection of papers entitled Harmonia Mensurarum (1722), which was published six years after his death.>>
Art Neuendorffer

User avatar
Joe Stieber
Science Officer
Posts: 157
Joined: Tue Aug 18, 2009 1:41 pm
Location: Maple Shade, NJ

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by Joe Stieber » Fri Apr 11, 2014 12:49 am

BDanielMayfield wrote:
orin stepanek wrote:I like the way Ceres and Vesta were circled; I never would have found them on my own! :D
Yes. I wonder what their apparent magnitudes are? Looks like they might be easy to find with binoculars.
I'm not certain when the picture was taken, but based on the positions of the asteroids and Mars, I'm guessing it would have been around April 3rd or April 4th. In that case, (4)Vesta is just below magnitude 6 and (1)Ceres is about magnitude 7, so they are indeed easy binocular objects, except where there is heavy light pollution. From my suburban home, it's no problem to see them with 10x42 binoculars (I've been following their movement for the past few weeks), but last night from center-city Philadelphia, it was difficult to see Vesta with 8x42 binoculars and I could not conclusively see Ceres (besides my center-city location amidst illuminated tall buildings, there was a gibbous moon in the sky and the asteroids were still somewhat low in altitude at 10 pm local time).

On the other hand, from a dark site, Vesta is visible with unaided eyes when it's near opposition (which it will be on April 13, 2014). I spotted it without optical aid on Sunday morning, April 6th, from the reasonably dark New Jersey Pine Barrens around 2 am, when they were near the meridian and after the moon had set. Vesta was at magnitude 5.8, which is within the nominal 6th magnitude limit for unaided eyes. One difficulty is the glare from nearby Mars -- it was necessary to use my outstretched hand to block it.

BDanielMayfield
Don't bring me down
Posts: 1968
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: Mars, Ceres, Vesta (2014 Apr 10)

Post by BDanielMayfield » Fri Apr 11, 2014 2:38 am

Thanks for that encouraging report Joe. I'll try to see these for myself, when the clouds allow.

Bruce
"Happy are the peaceable ... "