An artist impression of the mass-transfer phase followed by a double-detonation supernova that leads to the ejection of US 708. CREDIT: ESA/HUBBLE, NASA, S. GEIER
Scientists using the W.M. Keck Observatory and Pan-STARRS1 telescopes have discovered a star that breaks a speed record. This star is traveling at 1,200 km/sec (2.7 million miles per hour). Fast enough so the star will escape the gravity of the galaxy and leave. Only a handful of such stars are known.
This star was part of a binary star system and was ejected by a supernova explosion. The image above is an artist impression and it shows the star to the left and the supernova at the same time but the supernova would have faded away by the time the star hit that position.
The hypervelocity stars are destined to spend their lives speeding through intergalactic space although it is thought usually such stars get ejected due to a close encounter with the black hole at the center of Milky Way.
While the image shown here is an artist concept, scientists observed this star called US 708 with the Echellette Spectrograph and Imager instrument on the 10-meter, Keck II telescope to measure its distance and velocity along our line of sight. By combining position measurements from the archives with new measurements from Pan-STARRS1, scientists were able to come up with the star’s velocity across our line of sight. The trajectory of the star shows the velocity cannot be from an encounter with a black hole.
US 708 has another peculiar property in marked contrast to other hypervelocity stars: it is a rapidly rotating, compact helium star likely formed by interaction with a close companion. Thus, US 708 could have originally resided in an ultra compact binary system, transferring helium to a massive white dwarf companion, ultimately triggering a thermonuclear explosion of a type Ia supernova. In this scenario, the surviving companion, i.e. US 708, was violently ejected from the disrupted binary as a result, and is now traveling with extreme velocity.
A picture of the drilling section of Curiosity from the rover’s MAST cam. This is a raw image directly from the camera and not white balanced. Image Credit: NASA/JPL-Caltech/MSSS
A problem has developed with the Mars Science Laboratory also known as Curiosity.
The image above shows the drill section of the rover after it finished drilling into “Telegraph Peak” on 24 February 2015. On 27 February 2015 as the sample was being transferred the sample powder obtained from the drilling process an electrical “irregularity” triggered a fault-protection event. The fault-protection event halted the process because it stopped the arm activity.
Telemetry indicates a transient short circuit occurred prompting the pre-programmed response to the anomolous condition by stopping activity; hopefully sparing the rover further damage. Mission managers are running tests and will continue to work through the problem. In all likelyhood Curiosity will be back to work soon — stay tuned.
Rosetta’s shadow on Comet 67/C-G taken on 14 February 2015. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Here’s something you don’t see very often or ever for that matter. We can see the shadow of ESA’s Rosetta spacecraft on Comet 67P/Churyumov-Gerasimenko.
During the close flybys of a couple week ago, only 6 km separated spacecraft and comet. During the flyby the sun was directly between sun and comet so a shadow of about 20 x 50 meters (66 x 164 feet) was projected onto the comet. ESA was able to capture the image with the OSIRIS camera.
The pair were about 2.35 AU from the Sun so if I did the math correctly the light levels would be approximately 5.5 times less bright than what we see around us.
Approximate brightness relative to us is about the distance in AU (astronomical units) to the power of 2,
2.35 AU 2 = 5.5 (in this case 5.5 X dimmer)
Is this a first? I can’t think of any example of shadows on other comet encounters.
ESA has a nice write up and more pictures at the Rosetta blog, check it out.
The Dawn spacecraft is just days away from entering an orbit around the dwarf planet Ceres. The pictures are becoming better and more detailed raising anticipation for what we might learn. For starters, what makes the mystery bright spots bright and how was that “pancake” feature / crater formed? You can see the latter on the right hand image on the lower horizon and a nice view of it here (taken on 19 February 2015).
This image was taken on 25 February 2015 from a distance of 40,000 km / 25,000 miles.
The galaxy pictured here is NGC 4424, located in the constellation of Virgo. It is not visible with the naked eye but has been captured here with the NASA/ESA Hubble Space Telescope.
Although it may not be obvious from this image, NGC 4424 is in fact a spiral galaxy. In this image it is seen more or less edge on, but from above you would be able to see the arms of the galaxy wrapping around its centre to give the characteristic spiral form .
In 2012 astronomers observed a supernova in NGC 4424 — a violent explosion marking the end of a star’s life. During a supernova explosion, a single star can often outshine an entire galaxy. However, the supernova in NGC 4424, dubbed SN 2012cg, cannot be seen here as the image was taken ten years prior to the explosion. Along the central region of the galaxy, clouds of dust block the light from distant stars and create dark patches.
To the left of NGC 4424 there are two bright objects in the frame. The brightest is another, smaller galaxy known as LEDA 213994 and the object closer to NGC 4424 is an anonymous star in our Milky Way.
More Cere’s approach photo’s from Dawn. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Beyond the mystery spots of yesterday the Framing camera on the Dawn spacecraft took other photo’s of Ceres. I like the variation in the craters. A huge flat crater on the left and just above that another will what appear to be very sheer cliff edges. And the one on the right looks like it has kind of an odd crater right in front. Where is the big melt spot making a crater look like, well a crater?
These images of dwarf planet Ceres, processed to enhance clarity, were taken on Feb. 19, 2015, from a distance of about 29,000 miles (46,000 kilometers), by NASA’s Dawn spacecraft. Dawn observed Ceres completing one full rotation, which lasted about nine hours.
The images show the full range of different crater shapes that can be found at Ceres’ surface: from shallow, flattish craters to those with peaks at their centers. These views show sections of Ceres’ surface that are similar to those in PIA19056.
Dawn and Ceres closer than ever. Credit: NASA/JPL-Caltech/UCLA/MPS/ DLR/IDA/
The Dawn spacecraft returned this new image of Ceres taken from just 46,000 km / 29,000 miles.
The mysterious bright spot everybody (including me) has been speculating about turns out to be two bright spots The camera can’t resolve exactly what the spots are yet. There is some thought from the real experts to the idea the mystery spots are possibly of volcanic origin: “Ceres’ bright spot can now be seen to have a companion of lesser brightness, but apparently in the same basin. This may be pointing to a volcano-like origin of the spots, but we will have to wait for better resolution before we can make such geologic interpretations,” said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.
The terrain is very interesting too. Look at the “streak like” marks in the surface at the 4 o’clock region.
Make a new guess at the bright spot? Let’s see, how about this: the density of Ceres is a bit more than two so there ice down there. So maybe the object causing the crater blasted enough of the crust away exposing some kind of mantle of ice that is situated closer to the surface in some areas than others. I know, next week I’ll have a new theory. All part of the fun. Plus it is possible we could know by then, perhaps even probable.