Hubble Definition and 278 Threads

Hi all, this is my first post; apologies if it seems a bit basic, I suspect there's something fundamental I'm not getting here :smile: Say I observe the spectrum of a galaxy, and I calculate its redshift. I then use the Hubble Relation to find its distance, which is, say, ten billion light...

I am looking at inflation at the moment, and it says in my textbook that (aH)^(-1) is constantly increasing in matter or radiation dominated epochs. a is always positive and always increasing. This tells me that da/dt is positive. I think that setting the universe to MD/RD means that da/dt...

Some years ago I read that the Hubble Telescope is obsolete because modern telescopes have adaptive and corrective optics that make a space telescope unnecessary(at least for visible light). Since new Earth based telescopes have the advantage of very large mirrors(10 meters for the Keck) vs 2.4...

We normally assume that the recession of distant galaxies is due to the expansion of the space between the galaxies and us. In a co-moving frame the expansion of space is factored out so that all objects remain at a fixed distance away from us in cosmological time. Thus the co-moving frame is...

Homework Statement I should derive the Hubble law redshift from Maxwell equations in closed Universe. Homework Equations The metric of closed Universe is ds^2 = dt^2 - a^2(t)\left(d\chi^2 + \sin^2 \chi d\theta^2 + \sin^2 \chi \sin^2 \theta d\phi^2\right). The Hubble law redshift: \frac...

Does the measured value of the Hubble constant, H_0, depend on the details of the expansion model one uses?

i think Hubble constant is not a constant because of relativistic speeds of galaxies. is it?

Why will the Hubble parameter only decrease to .85 of today's Hubble parameter?

Hi, Let us assume that Hubble's Constant H is really constant. Therefore: a' / a = H where a is the scale factor. The solution to this equation is: a(t) = exp(H t) This equation describes an accelerating universe with deceleration parameter q given by: q = - a'' a / a'^2 =...

Hey, not sure if this is the correct forum but it seems physics will ultimately bring down the telescope. Why can't we leave the Hubble in space until it doesn't work anymore? It doesn't have any space crew to kill, it would break up on re-entree harming no-one and would continue to inspire our...

Dear all, I was reading about the Alcubierre drive, and although there's the more recent issue with Hawking radiation potentially frying everything within the warp field that's generated, I was wondering whether there had been any thought given to the possibility of the drive being flung parsecs...

As speed of galaxies is proportional to distance. Can we assume some galaxies have speeds grater than c? And do they have a negative time with a reference frame bound to earth? And the light they emit does it have red shift below cosmic background radiation? ...

For the most part I've been using the Hubble constant of: H0 = 72 km/s/Mpc but I've started seeing it expressed as: H0 = 100 h100 km/s/Mpc. what is h100 and why is it coming up in this?? I've also seen the critical density for the shape of the universe (flat/open/closed ect) as: Rhoc = 1.879...

As an assignment I am trying to calculate the Hubble redshift by looking at spectra of galaxies... Obviously the very first thing I want to do is find a suitable emission line...i am trying to find the halpha line in all the spectra I am analysing. First off, there is a very large spike in the...

What are the informations deducible from Hubble diagram of supernova 1a?

The above is taken from a paper by Wendy Freedman (http://www.pnas.org/content/96/20/11063.full.pdf) In 1999, she wrote that the Space Interferometry Mission (SIM), a project primarily focused on mapping the Milky Way and finding other Earth-like worlds, would provide parallax data that could...

I wasn't sure whether or not to post this in the Astronomy section but as this is homework, I decided to post it here. Homework Statement Suppose the Universe was much younger, eg 10,000 yrs old. Find the Hubble constant for such a Universe. Compare with the currently accepted value. What...

In other words why high redshift data is necessary for estimating the acceleration of universe?

Apologies in advance if this is a stupid question. I'm told the Hubble Deep Field shows galaxies as distant as 13 billion light years away. 13 billion years isn't far off the apparent age of the universe - 13.75 billion years, says Wikipedia, from estimates based on the Hubble constant...

Homework Statement I am working on a project for my cosmology course. I need to determine the Hubble constant from time delay in a gravitational lens. We are using QSO 0957+561 for our data. My question is how do I determine the relevant distances Dl, Ds? I have Dls already. The...

Hi everyone, First time posting, sorry if this is in the wrong format or wrong place. For a project in a cosmology course I need to find the Hubble constant from from time delay in a gravitational lens. the one we are using is QSO 0957+561. My question is how to I find the time delay from...

How can you mathematically calculate the Hubble constant at different redshifts? I know it's possible, and I can get the number by using the Cosmos Calculator: http://www.uni.edu/morgans/ajjar/Cosmology/cosmos.html But I want to know the equation they used to calculate the Hubble Constant...

An estimate of 0.94/tPlanck for the maximum reached by the Hubble parameter was given by Ashtekar and Sloan here (based on Loop qc): http://arxiv.org/abs/0912.4093 Loop quantum cosmology and slow roll inflation Abhay Ashtekar, David Sloan (Submitted on 21 Dec 2009) "In loop quantum cosmology...

Simple question hopefully. What was the initial value for the Hubble parameter immediately following the big bang (or ending of inflationary epoch)? I presume the initial velocity of expansion was lightspeed and started slowing from there.

This strange object was discovered by a Dutch schoolteacher who was scanning SDSS imges for Galaxy Zoo. http://www.science20.com/news_articles/hannys_voorwerp_one_strangest_space_objects_space_gets_hubble_treatment

Hi guys, Im just starting to get into viewing. I have a question about Mercury though. Can someone give me an idea of what mercury looks like from the Naked eye, binoculars, telescope, and hubble. Mainly I am trying to get what variations in colour, texture, surface details/features, are...

Student here, please forgive... I have a question about relativistic mass in galaxies. Is the mass of far away galaxies affected by expansion of universe? That is: Is mass of a far away galaxy is different for observer there compared to the observer here? Let's say there is a galaxy identical...

Suppose that some time in the future a clever group of theorists and experimentalists finally devise a way to accurately determine the value of the Hubble Constant. Say by an interferometer connected to a quantum computer. Everything works fine in the lab and is checked and checked...

Given the following parametric form of the Friedmann Equation for an open, dust-filled (matter-dominated) universe: a(x)={a_0 \Omega \over 2(1-\Omega)}(cosh(x)-1) t(x)={\Omega \over 2 H_0 (1- \Omega)^{3/2}}(sinh(x)-x) I am trying to calculate the Hubble Radius, R=c/H(t) where H(t)=(da/dt)/a...

I know this is dumb, but I'm just not getting any sort of intuition for what the "comoving Hubble radius" is. I have the definition in front of me in a book which says that it is equal to (in c = 1 units): (aH)-1 With a being the scale factor and H the Hubble parameter. So basically, it must...

Hi, I am just writing up my MSc thesis and want to explain the dimensionless Hubble parameter that I have been using through my work. I understand that you take the valuefor the Hubble "constant" and then divide by 100km/sec/Mpc to leave get a value which has no units. There seems to be...

I saw the IMAX Hubble film today. Whewww, It was absolutely beautiful! A must see for anyone who likes things.

I have a question that I could really use some help mathematically on. At its closest to Earth, Pluto is 28.6 AU from Earth. Can the Hubble Space Telescope distringuish any features on Pluto? Justify your answers using calculations. Please help! I know that the diameter of Pluto is...

Question: As an object approaches C and its length contracts, does space-time contract also, causing the a larger range of the universe to become visible? I.e. if the Hubble space telescope was traveling at high velocity, would it gain access to light from more distant galaxies than it has...

Homework Statement A galaxy is observed to be receding from the Sun with a velocity of 7500 km/s. The distance to the galaxy is determined to be 1.4×10^8 parsecs. From this observation, what is the value of the Hubble Constant (in km/s/Mpc)? Homework Equations The Attempt at a...

Hello! I want to get my data in terms of h70 -1 Sometimes the estimates are in terms of h50 or h70, and I know how to convert those just fine. However, sometimes they give H0 = 100 h Mpc-1 kms-1 instead... My question is, what is this in terms of h? I know that the relation is...

As the universe approaches perfect exponential expansion the Hubble constant approaches a limiting value. What is the limiting value and how long from now will it be reached?

I am reading conflicting interpretation of the Hubble constant in the exponentially expanding accelerating universe. Some say the Hubble constant is continuing to decrease; while others say Hubble constant is now unchanging and has become truly a constant. Which is correct?

Hubble "Staircase" effect? Hi, I was just wondering why some of the older Hubble pictures have a staircase effect on them? Any help would be appreciated! Example below edit: refer to examples in post #3

Hubble Ultra Deep Field "baby" galaxy examination It turns out that galaxies from over 12 billion years ago are anything but small and young. http://www.sciencedaily.com/releases/2005/10/051003233710.htm Is it possible that we got the age of the universe wrong, as it doesn't seem very...

Seeing the incredible images from the Hubble today really perplexed me. I am quite sure this is basic Physics, however I cannot find the answer anywhere on the Interweb :( My questions all have to do with peering farther back into time, by collecting light photons in some different or...

http://www.technologyreview.com/blog/arxiv/24491/ The paper has been out for a few days, but I didn't bother to look at it. Fortunately, it was spotted by techreview. http://arxiv.org/abs/0912.0535 A Cosmic Peek at Spacetime Foam Wayne A. Christiansen, David J. E. Floyd, Y. Jack Ng...

Could we set the natural value Hubble constant to be 1 in some calculation of cosmology, like what we do in the natural unit?

I've just started learning about Hubble, Red shifts, and how we measure the universe's expansion. It seems that he had two theories, that there is a stationary universe where the red shift from all light sources would be consistent or a theory in which the galaxies would be receding (and have...

New Images just released from Nasa- So happy we still have Hubble! They're everywhere on online, though You can find them on Youtube, at "Hubble Spectacular First Light Images in HD". cheers, joono

Which statement is true? A The apparent speed of recession of a galaxy is given by the product of the Hubble constant and the distance to the galaxy. B The further away a galaxy is, the lower its apparent speed of motion away from us. C A galaxy with a redshift of 5.37 is situated at a...

I never knew this before today but apparently NASA decided not to save Hubble because of the Columbia incident? Instead they are fitting it with a circular 'thing' that a rocket can latch onto to make Hubbles decent into Earth safe and away from inhabitated areas. I always thought that they...

what was the value of the Hubble parameter when the universe was decelerating?

Following different lines of reasoning (most likely all faulty) - I can convince myself that the current estimate(s) of the Hubble age may be off by a factor or 2 (more or less) depending upon the physiology asssumed for space and the model used to describe the expansion rate - specifically: If...

"...lowest scatter Hubble diagrams ever published" (Bailey et al) This is big news for cosmology. More accurate determination of distances and therefore of the Hubble parameter---a key proportion basic to the whole field. http://arxiv.org/abs/0905.0340 Using Spectral Flux Ratios to...