September 21, 2017

03.05.11: The Mysteries of Vesta.

A projected model of Vesta. (Credit: NASA/JPL/CALTech/UCLA/PSI).

In a string of recent firsts, scientists are about to get a good look at an enigmatic solar system body for the first time this summer. Launched in 2007, NASA’s Dawn spacecraft is due to orbit the asteroid Vesta in August of this year, giving us the first non-blurry close up images of the 530 kilometer diameter world. [Read more...]

AstroEvent(s): A Week of Moons, Tri-Conjunctions, & Lunar Features!

Venus, Vesta, & Pluto in a 5 degree field of view. (Created by Author in Starry Night).

This week offers a grab bag of unique events, far from the humdrum wide conjunctions and difficult to see pairings. The action starts on February 8th with a rare chance to see Saturn’s moons in 1 -8 order. This occurs in a narrow window from 19:01-19:38 UT, and thus favors the Asian Far East. The planet currently rises around 11PM local, and a majority of the moons should still be in order from your corresponding latitude. [Read more...]

17.01.11: Tracking Vestoids.

Vesta: Hubble’s best…(Credit: NASA/JPL/ESA/Space Telescope Institute).

The American Association of Variable Star Observers & NASA wants YOU to assist them with the up and coming Dawn mission. Specifically, scientists are looking to characterize “Vestoids,” or Vesta-like asteroids in preparation for Dawn’s exploration of the real thing in July of this year. To this end, the AAVSO has selected three targets for amateurs to observe; 1981 Midas (1973 EA), 4688 (1980 WF) and 137052 (1998 VO33). These Near Earth Objects (NEOs) are all thought to be very similar to the asteroid Vesta, and brightness estimates may constrain sizes and compositions. [Read more...]

AstroEvent: A Mutual Western Elongation.

January 8th, about a half hour before sunrise looking west from Tampa, Florida. (Created by the Author in Starry Night).   

One of the more unique events of 2011 occurs this weekend. The interior planets of Mercury and Venus both reach greatest western elongation within 24 hours of each other in the dawn skies. First, Venus reaches an elongation of 47° from the Sun on Saturday, January 8th at about 16:00UT/11:00 EST. Then, about 23.6 hours later, Mercury reaches the height of its morning apparition 23° west of the Sun. [Read more...]

AstroEvent: A Bright Dawn Comet.

 

Created with NASA/JPL Ephemeris generator).

Created with NASA/JPL Ephemeris generator).

 

   The dawn skies of October hold a special treat; a possible bright morning comet. 103/P Hartley 2 approaches perihelion on October 28, 2010. Earlier in the month sees it beginning its long dive through dawn skies. Northern hemisphere viewers will have the best view, as the comet passes through the constellations Cassiopeia, Perseus, Auriga, and Gemini in the month of October. [Read more...]

AstroEvent: A Challenging Dawn Conjunction.

Saturn & Mercury on closest approach. (Created by the Author with Starry Night).

Saturn & Mercury on closest approach. (Created by the Author with Starry Night).

 

   Set your alarm clocks; one of the closest but most challenging planetary pairings of the year happens this week in the early dawn skies. Mercury and Saturn will be within 1° degree of arc separation the morning of October 8th. Saturn is fresh from superior conjunction behind the Sun, and Mercury is currently undergoing a dawn apparition. Both will fit well in a binocular field of view or a low power eyepiece. The pairing will rise about 45 minutes prior to local sunrise, which for middle northern latitudes will occur around 7:45 AM local. [Read more...]

09.06.10: H2O in the Solar Neighborhood.

NASA's InfraRed Telescope Facility. (Credit: NASA/Institute for Astronomy).

NASA's InfraRed Telescope Facility. (Credit: NASA/Institute for Astronomy).

 

   Water, water, everywhere… over the past year or so, evidence for water in the solar system has been mounting in some unlikely places. The poles of our Moon. Ice geysers on Enceladus. Now add the denizens of our asteroid belt to the list; earlier this year, scientists at the Johns Hopkins University of Applied Physics in Laurel, Maryland have revealed findings that water ice may pervade the surface of asteroid 24 Themis. This comes from six years of careful study carried out by astronomers Andrew Rivkin and Joshua Emery using NASA’s Infrared Telescope Facility. By studying the asteroid of seven separate occasions, a definite signature pattern of water ice and carbonaceous organic materials has emerged. Much like the revelation of water hydroxyls on the Moon, this comes as something of a shocker; the asteroids bordering the inner solar were long suspected as being bone dry. 24 Themis orbits the Sun at a distance of 297 million miles, or about 3 A.U. “This is exciting because it provides us a better understanding about our past and our future,” stated Don Yeomans of NASA’s Near-Earth Object Program office at JPL. Clearly, the possibility of a “wet asteroid belt” may have further implications not only for space travel, but as to the origins of terrestrial water as well. Keep in mind, the ratios mentioned are often minuscule in an everyday sense; for example, the amount of water reckoned on the lunar surface during last years’ media blitz was on the order of one liter per ton of lunar regolith. Clearly, it will be a major technical feat to harvest such a small amount in useful quantities. Obviously, many sources of extraterrestrial water are still bone dry by the standards of the harshest terrestrial desert. Still, this tantalizing find may provide clues to fuel speculation as Dawn mission enroute to the asteroids Vesta and Ceres draws near; Vesta displays a curious reddish brown spectrum highly suggestive of a tarry surface, and Ceres has been proposed to perhaps harbor a subterranean ocean similar to what’s thought to exist beneath the surface of Jupiter’s large moon, Europa. This all begs for further exploration and could drive a new emphasis towards the President’s eluded to “Mission to an Asteroid” by 2030 or so… Apophis in 2029, anyone?

02.06.10: Dawn-A New Way to Explore the Solar System.

 

NSTAR electrostatic ion thruster under test. (Credit: NASA/JPL/Dawn).

NSTAR electrostatic ion thruster under test. (Credit: NASA/JPL/Dawn).

 

   An asteroid-bound spacecraft is also blazing a trail for technologies of the future. Dawn, NASA’s asteroid rendezvous mission blasted off from Cape Canaveral September 27th, 2007 enroute to explore the asteroids Ceres and Vesta starting next year. But unlike previous solar system missions, Dawn is able to do something that most interplanetary spacecraft can’t; change trajectories. Older traditional chemical rockets rely on their initial imparted thrust to get them on their way, but once that’s applied, the course is set. Beyond gravitational sling-shotting, little can be done to adjust their overall orbital paths, and you can’t park in orbit and visit interesting bodies, a major drawback. Dawn instead utilizes ion thrust engines. These provide a low thrust over a long period of time, rather than a chemical rockets’ high thrust in a short period of time. Although it requires Dawn a lengthy period to build up speed, its Xenon-solar powered drives ultimately win the race where specific impulse is concerned. This also enables it to carry a relatively light load of propellant. In fact, Dawn carries enough Xenon propellant for over 5 years of use. First proposed by none other than American rocket pioneer Robert Goddard in 1906, Ion based propulsion was first tested in 1959 at NASA, and utilized in the first  spacecraft aboard SERT-1 in 1964, and then more famously aboard Deep Space 1 in 1998. Many science fiction fans will remember the reference to ion drives in the original Star Trek episode “Spock’s Brain,” and the lineage can no doubt be traced further back in pulp Sci-Fi literature. Other spacecraft, such as the heroic Hayabusa returning to Earth next week and the proposed LISA Pathfinder, also utilize ion technology. Ion drive is well suited for asteroid exploration due to their low gravity fields, but in time missions bound for the major planets and moons could sport ion drives, as well. What Dawn will find as it nears the two asteroids is waiting to be seen; Vesta is a rocky terrestrial-type asteroid which may resemble early proto-solar material that formed rocky worlds like the Earth, and Ceres may even harbor a Europa-style environment, complete with ice enshrouded oceans! Dawn is scheduled to orbit Vesta for a year starting in July, 2011, and arrive at Ceres in February 2015. Perhaps, history will record that it was the ion-drive that truly opened up space exploration, and was ultimately how the solar system was won!