Explanation of ILRT's

The LA Times reported this weekend that astronomers can now explain intermediate luminosity red transients (ILRTs).  ILRT's are stellar bursts whose luminosities are between novae and supernovae.  They appear very red and are short-lived (STSCI).  Previously, some astronomers theorized that they result from two stars in a very close orbit that temporarily share a common envelope, referred to as a common envelope event or CEE, but there was no direct evidence (STSCI, Ivanova et al.).  Because CEE's are short-lived, astronomers thought it was improbable they would ever directly observe one, but in the paper by Ivanova et al., published Thursday in the journal Science¹, they propose a direct observational signature of a CEE, and these observations are in agreement with computer simulations based on the previous theories. 

I recommend the STSCI website provided below.  It provides more information than the LA Times article (also included), but is less technical than the paper published in the journal.  The paper has supplemental material available in the online version of Science.  This so far seems slightly more understandable, but it is very long.  It does have some cool computer simulations.  I have provided the link for that as well.

NOTE: if you have trouble accessing the supplemental material, you may need to be on campus or sign in to vpn through the UCR Libraries.  I also provided a link to view all the sources cited - some of them are free to download, so you don't have to sign in.

¹Identification of the Long-Sought Common-Envelope Events

N. Ivanova et al.

DOI: 10.1126/science.1225540

Science 339, 433 (2013)

Supplemental material and computer simulations: http://www.sciencemag.org/content/suppl/2013/01/23/339.6118.433.DC1

Space Telescope Science Institute (STSCI):  https://blogs.stsci.edu/newsletter/2011/11/21/miniworkshop-on-the-astrophysics-of-intermediate-luminosity-red-transients/

Click this link to see the LA Times article:  http://www.latimes.com/news/science/sciencenow/la-sci-sn-common-envelope-events-20130124,0,1637211.story?track=rss 

List of sources cited in the journal:  http://www.sciencemag.org/content/339/6118/433.full.html#ref-list-1

Comet 67P/Churyumov-Gerasimenko

Churyumov-Gerasimenko is a comet that orbits the sun every 6.6 years and the European Space Agency plans to land a spacecraft named Rosetta on its nucleus in November 2014.
Some interesting facts taken from the ESA website:
-The comet's perihelion distance was 4 AU before 1840 but due to encounters with Jupiter, it's perihelion distance is now 1.29 AU.
-Its nucleus is estimated at 5 by 3 km.
-It is unusually active for a short-period comet.
-Landing Rosetta on the comet will require four gravity assist maneuvers.

For all the details on the comet, click on this link: http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=14615
For the Rosetta mission information go here: http://sci.esa.int/science-e/www/area/index.cfm?fareaid=13

Comet ISON

Mark your calendar!  Comet ISON, now in Jupiter's orbit, will pass through the sun's atmosphere on November 28 this year.  It will be visible in the northern hemisphere and could potentially be bright enough to see in the day.  Check out this link, which includes a video.

http://science.nasa.gov/science-news/science-at-nasa/2013/18jan_cometison/

What Do Modern Astronomers Do?

It seems that much of modern astronomy requires data analysis and the use of computers to perform calculations and create models.  Astronomers no longer observe only in the visible spectrum – they use, for example, radio waves, UV and infrared to observe the universe.  This requires receivers and amplifiers to transmit signals/information which then has to be recorded, displayed and analyzed.  The information is often collected over time, as with the Wilkinson Microwave Anisotropy Probe (WMAP), which was launched in 2001 to measure the temperature of microwave background radiation, and streamed data through 2012¹.   

  As astronomers try to look at increasingly distant objects, interferometers have become widely used.  Two important examples are the CHARA array² at the Mount Wilson obervatory and LIGO³.  The CHARA array continously has research projects in progress, but the 60- and 100-inch telescopes are not as frequently used.  LIGO is a ground-based interferometer that was designed to detect gravitational waves.  In a lecture given by Kip Thorne, he stated that gravitational waves are the future of cosmology, along with numerical relativity (don’t ask, I did not understand anything about this part of his lecture.  All I know is it involves computing power).  He then showed a computer model prediction of what happens when two black holes collide.

So basically, my point in all this is that regardless of the field, I think astronomers spend less time looking at objects through a telescope and spend a lot of time waiting for data and then analyzing it and using computer models for simulations and predictions of things we cannot yet observe or test through experiment.

NOTE: I highly recommend checking out these sources for anyone not familiar with interferometers, particularly CHARA and LIGO.  These links contain basic explanations along with all the technical reports, so you can learn everything you could ever want to know from these sources.
¹ For more information on WMAP and radio astronomy, see NASA’s websites: http://map.gsfc.nasa.gov/
http://www2.jpl.nasa.gov/radioastronomy/radioastronomy_all.pdf

² http://www.mtwilson.edu/sci.php,

http://www.chara.gsu.edu/CHARA/techreport.php

³ http://www.ligo.caltech.edu/

BD+48 740

Hi all!  For my first post I wanted to share some news that I found interesting.  Last summer I came across a paper by Adamow, Niedzielski et al. reporting the discovery of a giant star believed to have recently engulfed a planet.  BD+48 740 is an evolved giant star that is unique for two reasons: it has an overabundance of lithium, and it has a planetary companion in a highly eccentric orbit.  It is rare for evolved giants to have a companion with a highly eccentric orbit and, according to the authors, even more rare is a lithium-rich red giant.  When a star leaves the main sequence and enters its red giant phase, the lithium abundance should drop.  They conclude that the most likely source of lithium overabundance is due to external contamination from a planetary companion.  They also conclude that the star previously had another planet in its orbit and explain the high eccentricity of the companion as a planet-planet scattering, sending one into the stellar surface and kicking the other into a more eccentric orbit.  The paper, titled BD+48 740—Li OVERABUNDANT GIANT STAR WITH A PLANET: A CASE OF RECENT ENGULFMENT?, can be found in the Astrophysical Journal Letters published 2012 July 20.

Source:

Adamow, M., Niedzielski, E., et al. 2009, ApJ, 754, L15, doi:10.1088/2041-8205/754/1/L15

For more information, see also:

Johnson, J. A. et al., ApJ, RETIRED A STARS AND THEIR COMPANIONS: EXOPLANETS ORBITING THREE INTERMEDIATE-MASS SUBGIANTS 665:785Y793, 2007

Villaver, E., Livio, M., 2009 ApJ, 705:L81–L85, 2009, doi:10.1088/0004-637X/705/1/L81