Hubble Uncovers the Farthest Star Ever Seen

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Hubble Uncovers the Farthest Star Ever Seen

Post by bystander » Mon Apr 02, 2018 4:28 pm

Hubble Uncovers the Farthest Star Ever Seen
NASA | GSFC | STScI | HubbleSite | 2018 Apr 02
More than halfway across the universe, an enormous blue star nicknamed Icarus is the farthest individual star ever seen. Normally, it would be much too faint to view, even with the world’s largest telescopes. But through a quirk of nature that tremendously amplifies the star’s feeble glow, astronomers using NASA’s Hubble Space Telescope were able to pinpoint this faraway star and set a new distance record. They also used Icarus to test one theory of dark matter, and to probe the make-up of a foreground galaxy cluster.

The star, harbored in a very distant spiral galaxy, is so far away that its light has taken 9 billion years to reach Earth. It appears to us as it did when the universe was about 30 percent of its current age.

The discovery of Icarus through gravitational lensing has initiated a new way for astronomers to study individual stars in distant galaxies. These observations provide a rare, detailed look at how stars evolve, especially the most luminous stars. ...

Hubble Discovers Most Distant Star Ever Observed
ESA Hubble Science Release | 2018 Apr 02
Click to play embedded YouTube video.
Astronomers using the NASA/ESA Hubble Space Telescope have found the most distant star ever discovered. The hot blue star existed only 4.4 billion years after the Big Bang. This discovery provides new insight into the formation and evolution of stars in the early Universe, the constituents of galaxy clusters and also on the nature of dark matter.

The international team, led by Patrick Kelly (University of Minnesota, USA), Jose Diego (Instituto de Física de Cantabria, Spain) and Steven Rodney (University of South Carolina, USA), discovered the distant star in the galaxy cluster MACS J1149-2223 in April 2016. The observations with Hubble were actually performed in order to detect and follow the latest appearance of the gravitationally lensed supernova explosion nicknamed “Refsdal” (heic1525)[1], when an unexpected point source brightened in the same galaxy that hosted the supernova. ...

The observed light from the newly discovered star, called Lensed Star 1 (LS1) was emitted when the Universe was only about 30 percent of its current age — about 4.4 billion years after the Big Bang. The detection of the star through Hubble was only possible because the light from the star was magnified 2000 times. ...

Hubble peers through cosmic lens to capture most distant star ever seen
University of California, Berkeley | 2018 Apr 02

Two Peculiar Fast Transients in a Strongly Lensed Host Galaxy - S. A. Rodney et al Extreme Magnification of an Individual Star at Redshift 1.5 by a Galaxy-Cluster Lens - Patrick L. Kelly et al Dark Matter under the Microscope: Constraining Compact Dark Matter with Caustic Crossing Events - Jose M. Diego et al
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Ann
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Re: Hubble Uncovers the Farthest Star Ever Seen

Post by Ann » Mon Apr 02, 2018 9:52 pm

This is just so fascinating! :D :jumping up and down:

Of course, me being me, I love the fact that this record-breaking star is a blue supergiant.

I find the spectrum of the star truly fascinating. It matches the spectrum of a blue supergiant like Rigel almost perfectly.
NASA wrote:

Scientists found that the Hubble data from MACS J1149+2223 Lensed Star 1 (Icarus) matches the model for a blue supergiant. The agreement shows a remarkably good fit, and indicates that Icarus is approximately twice as hot as the Sun.
If Icarus is a blue supergiant twice as hot as the Sun, it is another Rigel (or possibly slightly cooler than Rigel).

Rigel is not tremendously hot, some 12,000 K. If Icarus is of a similar temperature, it produces quite a lot of ultraviolet light, but still a lot less ultraviolet light than hotter blue supergiants, like Alnilam, the middle Orion's Belt star, or Zeta Puppis or Gamma Velorum.

I guess that Icarus is visible to Hubble because of its ultraviolet light, as that is distance-redshifted into the visible and infrared part of the spectrum?

Ann
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UCLA: Cosmic Quirk Helps Pinpoint the Farthest Star

Post by bystander » Wed Apr 04, 2018 2:25 pm

A Cosmic Quirk Helps Astronomers Pinpoint the Farthest Star Ever Seen
University of California, Los Angeles | 2018 Apr 03
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Re: Hubble Uncovers the Farthest Star Ever Seen

Post by neufer » Wed Apr 04, 2018 2:41 pm

Ann wrote:
Mon Apr 02, 2018 9:52 pm

Rigel is not tremendously hot, some 12,000 K. If Icarus is of a similar temperature, it produces quite a lot of ultraviolet light, but still a lot less ultraviolet light than hotter blue supergiants, like Alnilam, the middle Orion's Belt star, or Zeta Puppis or Gamma Velorum.

I guess that Icarus is visible to Hubble because of its ultraviolet light, as that is distance-redshifted into the visible and infrared part of the spectrum?
Well...visible, at least: A redshift of 1.5 makes a 12,000 K star look like 4,800 K [= 12,000/(1+1.5)].
Art Neuendorffer