APOD: Hitomi Launches (2016 Feb 18)

[APOD Robot]

Hitomi Launches

Explanation: On February 17 at 5:45pm JST this H-IIA rocket blasted skyward from JAXA's Tanegashima Space Center located off the southern coast of Japan, planet Earth. Onboard was the ASTRO-H X-ray astronomy satellite, now in orbit. Designed to explore the extreme cosmos from black holes to massive galaxy clusters, the satellite observatory is equipped with four cutting-edge X-ray telescopes and instruments sensitive to photon energies from 300 to 600,000 electron volts. By comparison, visible light photon energies are 2 to 3 electron volts. Following a tradition of renaming satellites after their successful launch, ASTRO-H has been newly dubbed "Hitomi", inspired by an ancient legend of dragons. Hitomi means "the pupil of the eye".

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[geckzilla]

Hopefully we get some images from Hitomi next time. We now have multiple x-ray observatories in orbit, but still just the one Hubble. Are they easier to make or something?

[NGC3314]

Hitomi's real strength should be in high-resolution spectroscopy. It carries a precision device which has been a long time coming - first it was slated for Chandra but was lost to a "descope"[1]. Then it was supposed to fly on Astro-E which would up in the Pacific due to booster failure. Then it was flown on Astro-E2 (Suzaku) but a cooling system failure (IIRC) shut it down before they could get any data. Fourth time a charm?

Each of these X-ray observatories does something new. The whole Hubble-replacement thing is tied to scientific as well as regular politics - for X-rays there is not non-space game, while in the optical there are often competing or complementary approaches to the science possible with big ground-based facilities. And the real successor, JWST, turned out to be technically more challenging and time-consuming than first estimated (which is why some astronomers think now is the time to seriously begin technical studies needed to something like the High-definition Space Telescope).

[1] Only on typing that did I realize what precise term "descope" is for loss of equipment to a space-astronomy mission when the money runs short. What happened to the giant primary mirror on my planet finder? I've been descoped!

[Chris Peterson]

Hopefully we get some images from Hitomi next time. We now have multiple x-ray observatories in orbit, but still just the one Hubble. Are they easier to make or something?

X-ray telescopes are harder to make. X-rays cover a vastly wider part of the spectrum than visible light, and very different optics and detectors are required to cover the full range. So x-ray observatories are either limited, or require multiple telescopes. Hitomi considerably extends the UV imaging and spectroscopic capabilities over the other instruments in orbit. In particular it will allow study of interstellar and intergalactic gas which isn't part of stars (which is most of the gas in the Universe).

We don't see a big push for more visible light telescopes in space because Hubble pretty much does the job. To some extent, we could say it has already done the job. It's a near perfect instrument, and can only be improved upon by increasing the size of the mirror. But that's expensive and arguably not going to yield much new science. We can perform much higher resolution visible light astronomy from the surface of the Earth than we reasonably can from space.

[NGC3314]

I'm going to have to argue with Chris on some of those points. There are indeed pushes for bigger optical/UV instruments (sample) - but to significantly improve on Hubble's performance, it has to be a big jump and a flagship-class mission that comes up in the budget only every 15-20 years (so, have it lined up on the runway when WFIRST is launched...) I strenuously object to the implication often found in instrument descriptions that we need them for a few key observations and then it's basically done - in every case of the Great Observatory-class missions, the unexpected (which builds up over time, and even accelerates as the community learns to do more challenging things and gets comfortable with large-scale programs) has been a greater legacy. Hubble Deep Field, the Andromeda survey, COSMOS survey of 2 square degrees - none of these would have been done in the first few years as people scrambled for low hanging fruit.

And I'm not convinced that visible-light adaptive optics is at the point to replace HST's optical capability. It may be possible, modulo needing to deconvolve PSF wings and the complications that introduces for spectroscopy, but I have not seen actual results yet matching <0.1" resolution for long exposures of faint targets shoreward of 0.8 microns or so. (Willing to see new data, of course).

Yes, a nerve!

[Chris Peterson]

I'm going to have to argue with Chris on some of those points. There are indeed pushes for bigger optical/UV instruments (sample) - but to significantly improve on Hubble's performance, it has to be a big jump and a flagship-class mission that comes up in the budget only every 15-20 years (so, have it lined up on the runway when WFIRST is launched...) I strenuously object to the implication often found in instrument descriptions that we need them for a few key observations and then it's basically done - in every case of the Great Observatory-class missions, the unexpected (which builds up over time, and even accelerates as the community learns to do more challenging things and gets comfortable with large-scale programs) has been a greater legacy. Hubble Deep Field, the Andromeda survey, COSMOS survey of 2 square degrees - none of these would have been done in the first few years as people scrambled for low hanging fruit.

And I'm not convinced that visible-light adaptive optics is at the point to replace HST's optical capability. It may be possible, modulo needing to deconvolve PSF wings and the complications that introduces for spectroscopy, but I have not seen actual results yet matching <0.1" resolution for long exposures of faint targets shoreward of 0.8 microns or so. (Willing to see new data, of course).

Yes, a nerve!

I'm just pointing out why non-visible-light instruments are currently attracting funding. A new visible light telescope would have to be much larger than HST to provide more than an incremental gain. Most visible light astronomy these days is focused (ha!) on very high resolution work that no space-based telescope is likely to match for decades or more. Meanwhile, here on Earth, we're building ever larger scopes that operate at ever higher resolutions- much greater than HST or any successor is likely to provide. Yes, these resolutions are only achievable over small fields, but that's primarily what people are interested in when it comes to very high resolution.

In the meantime, the really big holes in our observational capability are outside the visible light range.

[neufer]

Hopefully we get some images from Hitomi next time. We now have multiple x-ray observatories in orbit, but still just the one Hubble. Are they easier to make or something?

Hubble is way outperformed by visiting spacecraft on imaging the solar system
... though it does take excellent hires images of distant "schmuts":

[b][color=#0000FF]radio, infrared, optical, X-ray, and gamma-ray. (Click image for a larger version. Credits: radio: Haslam et al. 1982; infrared: NASA; optical: ESO/S. Brunier; X-ray: Max Planck Institute for Extraterrestrial Physics and S. L. Snowden; gamma-ray: NASA/DOE/Fermi LAT Collaboration)[/color][/b]

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Multiwavelength Astronomy

Radio:

• electrons moving in magnetic fields

Microwave:

• cool clouds of gas, including those around newly formed stars; the cosmic microwave background

Infrared:

• cool clouds of dust and gas; planets

Visible:

• planets, stars, some satellites

Ultraviolet:

• supernova remnants; very hot stars

X-rays:

• gas in clusters of galaxies; supernova remnants; stellar corona

Gamma-rays:

• accretion disks around black holes

[daddyo]

Looking at your gamma ray image with the note that they eminate from black hole accretion disks, it makes it look like our galaxy is loaded with black holes.

[Chris Peterson]

Looking at your gamma ray image with the note that they eminate from black hole accretion disks, it makes it look like our galaxy is loaded with black holes.

I'm sure our galaxy is loaded with black holes. But they represent only one source of gamma rays.

[GaryG]

Congratulations to Jaxa!

[geckzilla]

I confess that my comment was made merely to stimulate some discussion on an otherwise "unpopular" APOD image. Thanks for humoring me.

[Ann]

Looking at your gamma ray image with the note that they eminate from black hole accretion disks, it makes it look like our galaxy is loaded with black holes.

I'm sure our galaxy is loaded with black holes. But they represent only one source of gamma rays.

The brightest X-ray source in our galaxy seems to be the Vela pulsar. But the Vela pulsar appears to be visible as a discrete source in gamma rays, too. And since the Vela pulsar is not a black hole, it seems reasonable to assume that other X-ray sources might produce some gamma rays, too.

Ann