Ojo de la Cerradura

sayitwithscience: Variable Star Astronomy Variable stars are...

alexcunn — Mon, 14 Nov 2011 19:11:12 -0400

Variable Star Astronomy

Variable stars are stars whose brightness changes because of physical changes within the star. There exist more than 30,000 variable stars in just the Milky Way. Variable star astronomy is a popular part of astronomy because amateur astronomers play a key role. They have submitted thousands of observed data and these data are logged onto a database. American readers can find information on it on the American Association of Variable Star Observers page.

One of such variable stars are called Cepheids. Cepheids are pulsating variable stars because they undergo a “repetitive expansion and contraction of their outer layers” [1]. In Cepheids, the star’s period of variation (about 1-70 days) is related to its luminosity; the longer the period, the higher the luminosity. In fact, when graphed, the relationship is shown by a straight line (as can be seen on the title image). Henrietta Swan Leavitt, an American astronomer, first discovered this and understood the significance of this knowledge. Combined with understanding of the star’s apparent magnitude (a previously written post on this subject can be found here), astronomers can use this information to find a star’s distance from Earth. Cepheids are famously known for their usefulness in finding distances to far-away galaxies and other deep sky objects. Leavitt died early from cancer but was to be nominated for the Nobel Prize in Physics by Professor Mittag-Leffler (Swedish Academy of Sciences).

Edwin Hubble used Leavitt’s discovery to prove that the Andromeda Galaxy (M31) is not part of the Milky Way, but was able to find the distance to the Andromeda Galaxy (between 2-9 million light years away). At first his calculation was incorrect (900,000 light years) because he observed Type I (classical) Cepheid Stars. Type I Cepheid stars are brighter, newer Population I stars. Hubble later used type II Cepheids (also called W Virginis stars), which are smaller, dimmer, Population II stars, and he was able to make more accurate calculations.

To determine the star’s distance, use the inverse square law of light brightness.

A similar type of star are RR Lyrae Variable Stars. They are smaller than Cepheids and have a much shorter period (from a few hours to a day). On the other hand, they are far more common. Likewise, they can be used to solve for distances as well. Low mass stars live longer, and thus Cepheid stars are generally younger because they are more massive.

Both Cepheids and RR Lyrae Variable stars are referred to as standard candles: objects with known luminosity. If you’ve ever wondered how astronomers came to those enormous figures when describing how far away galaxies and stars are from us, you can now better understand why and how.

skepttv: Star Classification - Sixty Symbols The Sun is...

alexcunn — Wed, 18 May 2011 22:24:58 -0300

skepttv:

Star Classification - Sixty Symbols

The Sun is designated as a “G2V” star. What does that mean?

via incomprehensibleuniverse

GM=tc^3: Old, Old Galaxy UDFj-39546284

alexcunn — Sun, 30 Jan 2011 19:31:39 -0400

GM=tc^3: Old, Old Galaxy UDFj-39546284

Photo

alexcunn — Sat, 27 Nov 2010 16:01:03 -0400

Partículas WIMP de materia oscura ocho veces más pesadas que el...

alexcunn — Sun, 24 Oct 2010 20:26:10 -0300

Partículas WIMP de materia oscura ocho veces más pesadas que el protón observadas en el centro de la Vía Láctea « Francis (th)E mule Science’s News

Dan Hooper, físico del Fermilab, y Lisa Goodenough, postgraduada de la Universidad de Nueva York, han descubierto pistas de la existencia de materia oscura en el centro de la Vía Láctea gracias al análisis de los datos observados por el Telescopio Espacial Fermi de rayos gamma. El único origen razonable es la aniquilación en un par de tauones de una partícula tipo WIMP con una masa en el rango de 7’3 a 9’2 GeV/c², unas ocho veces más pesada que el protón, con un error del 10%.

SKY-MAP.ORG / WIKISKY

alexcunn — Mon, 18 Oct 2010 20:27:43 -0300

SKY-MAP.ORG / WIKISKY

Top 10 Deep-Space Photos From Infrared Telescope’s Final Days |...

alexcunn — Sat, 09 Oct 2010 10:59:47 -0300

Top 10 Deep-Space Photos From Infrared Telescope’s Final Days | Wired Science | Wired.com

APOD: 2010 October 3 - Io in True Color

alexcunn — Tue, 05 Oct 2010 20:08:14 -0300

APOD: 2010 October 3 - Io in True Color

ESO - ann1062 - ESOcast 21: The Great Observatories Origins Deep...

alexcunn — Mon, 27 Sep 2010 12:10:26 -0300

ESO - ann1062 - ESOcast 21: The Great Observatories Origins Deep Survey (GOODS)

scienceisbeauty: Electromagnetic Spectrum according to XKCD

alexcunn — Tue, 06 Jul 2010 14:51:27 -0300

scienceisbeauty:

Electromagnetic Spectrum according to XKCD

spacethebeyond: (via:unknownskywalker) Supernovae mystery...

alexcunn — Sat, 03 Jul 2010 10:36:51 -0300

spacethebeyond:

(via:unknownskywalker)
Supernovae mystery solved

Supernovae are gigantic stellar explosions that can be seen across the entire universe. Type Ia supernovae are a relatively homogeneous class of stellar explosions, which researchers use as ‘standard candles’ to observe the acceleration of the universe.

It has long been known, however, that they exhibit considerable variation in their spectra and the origin of the differences has been unknown. Now scientists have shown that supernovae explode asymmetrically and the difference in their appearance is simply due to the directions from which the supernovae are being observed.

There is now broad consensus that the relative homogeneity of type Ia supernovae is due to their having the same origin, namely a white dwarf in a binary system, absorbing material thrown out from its companion star, and when it reaches 1.4 solar masses it explodes as a supernova.

Supernovae that fade in the same way may exhibit quite different behaviour in how fast their expanding material slows down (the so-called velocity gradient). With new detailed studies, scientists have now shown that the velocity gradient is closely associated with these supernovae exploding asymmetrically, where the ignition takes place away from the centre. So the different appearances of the supernovae simply depend on the point of view they are observed from.

Type Ia supernovae have played a crucial role in cosmology because they can be used to measure the distances across the universe. The results give new insight into how these stars explode and solving the problem with their different appearances, and also brings good news for the use of ‘standard candles.’

Image: A schematic picture of the structure of a supernova Ia. The ashes of the first phases of the explosion, right after ignition (yellow), are offset with respect to the centre of the ejected material. Depending on where we view the supernova from, it will demonstrate different spectral properties.

Source: Niels Bohr Institute | See also: SPACE.com

cosmicpower: jipc:dvdp: When a coronal mass ejection (CME)...

alexcunn — Wed, 16 Jun 2010 17:46:50 -0300

cosmicpower:

jipc:dvdp:

When a coronal mass ejection (CME) erupts from the Sun, movies in extreme ultraviolet light often show enormous waves, spreading over a large area on the solar surface, just as tsunamis travel far from the original seismic event. Now STEREO data have been used to show that these waves are the footprints of giant domes that spread upward into the corona as well as outward across the surface.

scienceisbeauty: 2MASS (Two Micron All Sky Survey) Galaxy...

alexcunn — Sun, 13 Jun 2010 13:58:00 -0300

scienceisbeauty:

2MASS (Two Micron All Sky Survey) Galaxy Redshift Catalog (XSCz)

Credit&Source: Thomas H. Jarrett, Infrared Processing and Analysis Center, 4-D Visualization of the XSCz with Partiview

fuckyeahnebulas: Flame Nebula, Horsehead Nebula, Running Man...

alexcunn — Sun, 13 Jun 2010 13:52:09 -0300

fuckyeahnebulas:

Flame Nebula, Horsehead Nebula, Running Man Nebula & Orion Nebula

fuckyeahnebulas: Eta Carinae Nebula

alexcunn — Sun, 13 Jun 2010 13:46:01 -0300

fuckyeahnebulas:

Eta Carinae Nebula

spacethebeyond: itsfullofstars: Orange Sun SimmeringCredit...

alexcunn — Sun, 13 Jun 2010 12:53:38 -0300

spacethebeyond:

itsfullofstars:

Orange Sun Simmering
Credit & Copyright: Alan Friedman (Averted Imagination)

Explanation: Even a quiet Sun can be a busy place. And over the deep Solar Minimum of the past few years, our Sun has been unusually quiet. The above image, taken last week in a single color of light called Hydrogen Alpha and then false colored, records a great amount of detail of the simmering surface of our parent star. The gradual brightening towards the Sun’s edge in this color-inverted image, called limb darkening, is caused by increased absorption of relatively cool solar gas. Just over the Sun’s edges, several prominences are visible, while two prominences on the Sun’s face are seen as light streaks just above and right of the image center. Two particularly active areas of the Sun are marked by dark plages. In contrast to recent quiet times, our Sun is moving toward Solar Maximum, and for years will likely appear much more active.

(via APOD)

cosmicpower: invaderxan: Exploding White Dwarf Star A white...

alexcunn — Sun, 13 Jun 2010 12:46:18 -0300

cosmicpower:

invaderxan:

Exploding White Dwarf Star

A white dwarf is what stars like our Sun become after they have exhausted their nuclear fuel. Near the end of its nuclear burning stage, such a star expels most of its outer material, creating a planetary nebula. Only the hot core of the star remains. This core becomes a very hot (T > 100,000K) young white dwarf, which cools down over the course of the next billion years or so.

Source: Berkeley Lab Computing Sciences, Image Gallery

(via scienceisbeauty)

cosmicpower: Perhaps the original spiral nebula, M51 is a large...

alexcunn — Sun, 13 Jun 2010 12:45:08 -0300

cosmicpower:

Perhaps the original spiral nebula, M51 is a large galaxy, over 60,000 light-years across, with a readily apparent spiral structure. Also cataloged as NGC 5194, M51 is a part of a well-known interacting galaxy pair, its spiral arms and dust lanes clearly sweeping in front of companion galaxy NGC 5195 (top). This dramatically processed color composite combines M51 image data from the Calar Alto Observatory’s 1.2 meter telescope. The data include long exposures through a narrow hydrogen alpha filter that trace emission from atomic hydrogen. Reddish hydrogen emission regions, called HII regions, are the regions of intense star formation seen to lie mainly along M51’s bright spiral arms. Intriguingly, this composite also shows red hydrogen emission structures in the faint features extending even beyond NGC 5195, toward the top of the frame.

proofmathisbeautiful: scienceisbeauty: Integrating the planck...

alexcunn — Fri, 21 May 2010 19:41:48 -0300

proofmathisbeautiful:

scienceisbeauty:

Integrating the planck curve shows that the total energy of a star depends on the fourth power of its blackbody temperature.

Source: Basic Stellar Properties, The Electronic Universe, University of Oregon

Astronomy Picture of the Day

alexcunn — Mon, 03 May 2010 21:35:09 -0300

Astronomy Picture of the Day